Definition: PL/I

(Programming Language 1) A high-level IBM programming language introduced in 1964 with the System/360 series. It was designed to combine features of and eventually supplant COBOL and FORTRAN, which never happened. A PL/I program is made up of procedures (modules) that can be compiled independently. There is always a main procedure and zero or more additional ones. Functions, which pass arguments back and forth, are also provided.